title: Purification and biochemical properties of a cytochrome bc complex from the aerobic hyperthermophilic archaeon Aeropyrum pernix.
abstract: BACKGROUND
  The bioenergetics of Archaea with respect to the evolution of electron transfer systems is very interesting. In contrast to terminal oxidases, a canonical bc1 complex has not yet been isolated from Archaea. In particular, c-type cytochromes have been reported only for a limited number of species.
  
  
  RESULTS
  Here, we isolated a c-type cytochrome-containing enzyme complex from the membranes of the hyperthermophilic archaeon, Aeropyrum pernix, grown aerobically. The redox spectrum of the isolated c-type cytochrome showed a characteristic α-band peak at 553 nm corresponding to heme C. The pyridine hemochrome spectrum also revealed the presence of heme B. In non-denaturing polyacrylamide gel electrophoresis, the cytochrome migrated as a single band with an apparent molecular mass of 80 kDa, and successive SDS-PAGE separated the 80-kDa band into 3 polypeptides with apparent molecular masses of 40, 30, and 25 kDa. The results of mass spectrometry indicated that the 25-kDa band corresponded to the hypothetical cytochrome c subunit encoded by the ORF APE_1719.1. In addition, the c-type cytochrome-containing polypeptide complex exhibited menaquinone: yeast cytochrome c oxidoreductase activities.
  
  
  CONCLUSIONS
  In conclusion, we showed that A. pernix, a hyperthemophilic archaeon, has a "full" bc complex that includes a c-type cytochrome, and to the best of our knowledge, A. pernix is the first archaea from which such a bc complex has been identified. However, an electron donor candidates for cytochrome c oxidase, such as a blue copper protein, have not yet been identified in the whole genome data of this archaeon. We are currently trying to identify an authentic substrate between a bc complex and terminal oxidase.
authors.affiliation: Department of Bioscience and Bioinformatics, Kyushu Institute of Technology, Kawazu 680-4, Iizuka, Fukuoka-ken 820-8502, Japan.
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Kabashima
authors.forename: Junshi
authors.initials: J
authors.lastname: Sakamoto
mesh_terms: D041522:Aeropyrum / Q000201:enzymology*; D019843:Archaeal Proteins / Q000302:isolation & purification / Q000378:metabolism*; D003574:Cytochrome c Group / Q000302:isolation & purification / Q000378:metabolism; D014450:Electron Transport Complex III / Q000302:isolation & purification / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000302:isolation & purification / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D013058:Mass Spectrometry
chemical_list: D019843:Archaeal Proteins; D003574:Cytochrome c Group; C083951:cytochrome c553; D003576:Electron Transport Complex IV; D014450:Electron Transport Complex III